1. Field of the Invention
The present general inventive concept relates to an image forming apparatus and a control method thereof, and more particularly, to an image forming apparatus and a control method thereof, in which a phase of an alternating current (AC) power is detected to perform a fusing control.
2. Description of the Related Art
An image forming apparatus, such as a printer, a multi-function peripheral, etc., forms an image on a recording medium, such as paper or the like, etc., based on image data such as a document, a photograph, etc. In a case of an electrophotographic type image forming apparatus such as a laser printer, a toner which is developed on a photoconductive drum is transferred to and fused on a recording medium, to thereby form an image. In this case, the image forming apparatus includes a fusing unit to fuse the toner at a high temperature.
FIG. 1 shows a schematic diagram of a configuration of a conventional image forming apparatus 1. The image forming apparatus 1 includes an image forming unit 11 to form an image, and the image forming unit 11 includes a fusing unit 11a which is provided with a heater (not illustrated) for fusing. The image forming apparatus 1 further includes a power supply 12 to supply electric power to the fusing unit 11a, and the power supply 12 includes a triac 12a to perform a switching operation in order to control a temperature of the fusing unit 11a. Also, the image forming apparatus 1 further includes a controller 13 to control the switching operation of the triac 12a. The controller 13 controls the triac 12a based on a phase of an alternating current (AC) power which is supplied from the power supply 12, and thus the image forming apparatus 1 includes a phase detector 14 to detect the phase of the AC power.
Further, the power supply 12 includes a relay 12b to cut off the power supplied to the fusing unit 11a, thereby minimizing a power consumption of the triac 12a in a standby mode which the image forming apparatus 1 enters when not being used.
FIG. 2 illustrates a relay 12b and a phase detector 14 in a conventional image forming apparatus 1. As illustrated in FIG. 2, the relay 12b is provided on a power supplying path between an AC power source and the fusing unit 11a, and turns on/off based on a relay control signal. If the image forming apparatus 1 operates normally, the relay 12b is turned on so that the AC power can be supplied from the power supply 12 to the fusing unit 11a. However, if the image forming apparatus 1 enters the standby mode, the relay 12b is turned off so that the AC power cannot be supplied from the power supply 12 to the fusing unit 11a. 
However, in the conventional image forming apparatus 1, since the phase detector 14 is placed downstream of the relay 12b, the phase detector 14 cannot properly detect the phase of the AC power when the relay 12b is turned off and the AC power is not supplied to the fusing unit 11a and the phase detector 14. Particularly, in the standby mode, the conventional image forming apparatus 1 is required to monitor whether the AC power is supplied or not and perform a data backup, a system reset (i.e., a central processing unit (CPU) reboot) or the like operation if the AC power is cut off, but it cannot do that since the relay 12b is turned off.
To solve this problem, the phase detector 14 is placed upstream of the relay 12b opposite to the one end, such that it is possible to detect the phase of the AC power, however there is still a problem of satisfying a constraint that power which is consumed in the standby mode should not exceed a predetermined electric power (e.g., 1 W). Conventionally, the phase detector 14 includes a plurality of diodes and resistors, therefore it is difficult for this configuration to satisfy a desired constraint on power consumption.
Nonetheless, precise phase control is continuously needed in a normal mode as well as during the standby mode, and thus an image forming apparatus 1 which meets such a need is desired.